1. Field of the Invention
The present invention relates to improvements in push button type fasteners wherein the fastener can be both quickly installed and released.
2. Description of the Prior Art
Many systems wherein at least two members are mechanically joined require that the members be capable of being fastened together and separated quickly and simply for maintainability purposes. For example, in the assembly of an automotive airbag to the steering column and wheel, the airbag mechanism typically is attached by four screws that are threaded into tubular standoffs that are attached to a plate that the airbag is secured to. As the airbag is one of the last items to be assembled on the almost finished vehicle, its accessibility is very limited. Therefore the time required to assemble the airbag to the steering wheel assembly is longer than desired because the screws have to be inserted from behind the steering wheel. The convenience of installation is severely hampered due to the natural obstructions that accompany any automobile such as a gear selector lever, the turn signal stalk, the steering wheel post shroud and the proximity of the dashboard. The installation may also require the steering wheel to be rotated to a certain position in order to access all four holes; in addition the aligning of the screw to its mating threads in a blind application is difficult. The same problems occur during the check out cycle if a malfunction occurs or at a later time during normal servicing at the dealer's facility. The current practice of locating the holes for the airbag assembly and to install the four screws is slow and expensive.
The reduction in time required to remove the installed airbag, i.e., due to a mechanical defect or after deployment is more than desired due both to the absence of a trained mechanic who normally installs airbags and to the cramped quarters which prohibits the use of power tools. The current time consuming system thus requires rotation of the steering wheel to certain positions to provide access and the unloosening and removal of the four screws.
A number of fastener assemblies for joining two members together which does not require the use of a nut are available in the prior art. For example, U.S. Pat. No, 5,011,355 to Motoshige discloses a pushbutton type fastener which utilizes a stud assembly snap-fitted into one of two panels to be joined, a mating socket being snap fit to the other panel. The two components are secured together by pushing a stud in the stud assembly toward the socket. The stud assembly is released from the socket by rotating the stud enabling a spring to urge the stud out of its engagement with the socket.
Although the pushbutton fastener of the type illustrated in the Motoshige patent satisfactorily performs its function of releasably joining two panels together, the fastener requires a number of mechanical parts to perform its function, thus increasing its cost and complexity. In addition, certain applications, such as the airbag installation/maintenance procedure noted hereinabove, requires access to the rear (non-head) portion of the fastener assembly to release it. Since the Motoshige type pushbutton fastener is releasable by rotating the head portion of the stud portion of the stud assembly, it would not be adaptable for use in that application.
The fastener disclosed in U.S. Pat. No. 5,207,544 addressed the above problem by providing a push button type fastener that requires fewer components and wherein panels joined together by the fastener can be quickly released by accessing the fastener at the end opposite its head portion, features which are useful in many applications.
In many situations, testing parameters are often established to simulate as closely as possible the perceived environment the fastener may be exposed to during the life cycle of the product in which the fastener is utilized. These test parameters may include extra tests, such as high frequency, long period vibration tests, in addition to those normally required.
In order to ensure that the locking ball members described in the aforementioned patent are prevented from extracting themselves from the operating position if the product is ever subjected to vibrations which exceed the specified limits in time and frequency, it is desired to provide a mechanism which accomplishes this in a relatively simple and inexpensive manner.